Nearly 20 years ago, as I wandered as a newspaper reporter from tent to tent at the Global Forum in Rio de Janeiro’s Flamingo Park, with young, idealistic environmental activists milling about, I couldn’t help thinking of Dale Arden’s line from the film Flash Gordon, a decade before: “Flash, Flash, I love you, but we only have 14 hours to save the Earth!”

Brazil’s 1992 Earth Summit was in full swing, and when it closed it even seemed that we would manage to save the world from global warming, and species extinction too. After all, delegates at the United Nations Conference on Environment and Development — as it was officially known — had just adopted two conventions to stave off these threats.